Excuse me; I am going out on a limb here. If it were me, I would CAREFULLY use a very small amount of crazy glue (cyano acrylate). By placing a very small drop of it on the internal most edge of the crack, you can keep the wound from spreading. Mind you, this is a delicate procedure, and ducks don't like to hold still. But this glue was originally developed for wounded soldiers in Viet Nam. The medics could apply some glue, and slap the skin together--and it would hold! At least long enough to med-evac them back to a hospital unit.
Again, I would do this. Whatever you do, it is up to you. Just don't grease up the area with vaseline-based ointments!! Then nothing will ever stick to it.
Again, if I could get a tongue depressor or popsicle stick into his mouth, and then hold the beak closed--that is when I would do the application. And I would hold it until the glue had crosslinked. This type of glue is activated by humidiy in the air. If it is a very dry day, I wouldn't try it, since the glue would take forever to set up. But in humid conditions, it could kick off right away.
Now, after all that long winded description, it is up to you to be super observant. If the bill seems stable over a couple of days, I agree with doing nothing, and letting it heal on it's own. But if the crack is continuing to go deeper--that is when I would use the glue to stop the propagation of the cracking.
Good luck, and godspeed.
Friend
Spirit
Educator
